The present invention relates broadly to flexible laminates having aesthetically pleasing facing layers and is more particularly concerned with a resiliently padded laminate construction suitable for use in the preparation of aesthetically faced injection molded thermoplastic articles.
Automotive interior trim articles, such as door panels, door and window pillars, armrests, instrument panels, seat backs, seat side panels, consoles, sun visors and the like typically comprise some form of shaped relatively rigid support structure having an aesthetically pleasing facing secured to at least those surfaces thereof which are exposed to the interior of the vehicle.
There has recently been developed a composite injection molding technique whereby, in a single step, a non-woven fabric facing may be secured directly to the surface of a thermoplastic support structure during injection molding thereof. In accomplishing this method a non-woven fabric facing material is first treated by needle punching so as to provide multiple sites of entry for the thermoplastic melt injected into the mold. The fabric is cut into a suitably sized and shaped facing element, the needled, non-woven fabric element placed into the female half of the mold, the mold closed, and a precise volume of a molten thermoplastic resin injected into the mold cavity under relatively low pressure of, say, less than about 1000 p.s.i., such that the molten resin fills the mold gently with an even, uniform melt front to form the support structure. In addition, the injected molten resin migrates through the back of the needled non-woven fabric facing element, filling the interstices of the fabric fibers to a predetermined uniform depth and thereby securing the non-woven fabric facing element to the surface of the injection molded thermoplastic support structure. Utilizing this process automotive trim articles comprising, for instance, a non-woven polyester fabric facing material secured to variously shaped injection molded polypropylene support structures have been successfully fabricated. Further details regarding this process can be had, for instance, by reference to the article: "New Composite Molding Method", Siebolt Hettinga, Fiber World, September 1992, pgs. 2, 4, 8 and 9. While the foregoing injection molding technique is capable of producing excellent quality aesthetically faced thermoplastic articles, it is possessed of certain limitations. Primarily, the method requires that a non-woven type fabric be utilized as the facing material or, at the least, that a non-woven type of fabric be employed as the backing layer in a laminate facing structure. This is so because the process inherently depends upon at least some significant migration of the injected thermoplastic resin into the interstices of the non-woven material in order to establish a mechanical keying of the material to the molded support structure.
It is often a desideratum of the industry that injection molded thermoplastic automotive trim articles be faced with an aesthetically pleasing, resiliently padded laminate, such that the surface(s) of such trim articles exposed to the vehicle occupants not only be aesthetically pleasing from a visual standpoint, but also afford a pleasing soft tactile sensation or "hand", or even significant impact energy absorption properties. To this end, facing laminates have been prepared comprising an aesthetically pleasing facing layer composed of a woven, non-woven or knit fabric or leather or an embossed or grained surface thermoplastic, an intermediate soft resilient thermoset or thermoplastic cellular polymer foam layer to confer the soft feel or "hand" to the overall construction, and a needled non-woven fabric backing layer to provide a keying surface into which an injection molded thermoplastic can migrate and secure the laminate to an injection molded support structure prepared in accordance with the relatively low pressure injection molding process outlined above. Utilizing such laminates it has been possible, on occasion, to successfully produce certain good quality injection molded automotive trim articles having at least one surface defined by an aesthetically pleasing, resiliently padded, facing laminate. However, one of the difficulties encountered in attempting to adapt such padded facing laminates and the foregoing injection molding technique to conventional injection molding production lines resides in the experience that there often occurs, in a non-uniform or unpredictable manner, localized in-mold physical collapse or degradation of portions of the intermediate cellular polymer layer of the facing laminate, thereby causing one or more visibly apparent underlying defects in the resiliently padded fabric surfaces of the resulting injection molded articles. Too, where such partial or complete collapse of portions of the polymer foam layer of the laminate occurs, there obviously also occurs in said portions a degradation of the desired soft hand or feel properties of the construction. An additional problem has also been noted where the laminate comprises an embossed or grained thermoplastic facing layer. Here, the heat and pressure experienced by the laminate in forming the support structure has resulted in a technically and aesthetically undesirable ironing or smoothing of the embossed or grained exterior surface of the facing layer. In accordance with the present invention these problems have been solved or, at the least, substantially ameliorated.